/**
 * Copyright (c) 2010 by Kevin Bierhoff.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *    1. Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *    2. Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *    3. Neither the names of the authors nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.googlecode.syper.javasyp.formulae;

import java.util.Collections;
import java.util.List;

/**
 * @author kevin
 * @since May 9, 2010
 */
public class Quantifier implements Formula {

	public static Formula exists(Local var, Formula body) {
		return exists(Collections.singletonList(var), body);
	}

	public static Formula exists(List<? extends Local> vars, Formula body) {
		if (vars == null || vars.isEmpty())
			return body;
		return new Quantifier(true, vars, body);
	}

	public static Formula forall(Local var, Formula body) {
		return forall(Collections.singletonList(var), body);
	}

	public static Formula forall(List<? extends Local> vars, Formula body) {
		if (vars == null || vars.isEmpty())
			return body;
		return new Quantifier(false, vars, body);
	}

	private final boolean isExists;
	private final List<? extends Local> vars;
	private final Formula body;

	public Quantifier(boolean isExists, List<? extends Local> vars, Formula body) {
		super();
		if (vars.isEmpty())
			throw new IllegalArgumentException("Vacuous quantifier: " + vars);
		this.isExists = isExists;
		this.vars = vars;
		this.body = body;
	}

	public boolean isExists() {
		return isExists;
	}

	public boolean isForall() {
		return ! isExists;
	}

	public List<? extends Local> getVars() {
		return vars;
	}

	public Formula getBody() {
		return body;
	}

	@Override
	public <T> T dispatch(FormulaVisitor<T> visitor) {
		return visitor.visit(this);
	}

	@Override
	public boolean isBoolean() {
		return true; // quantifiers are always true
	}

	@Override
	public String toString() {
		String q = isExists ? "exists " : "forall ";
		return q + vars + ": " + body;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((body == null) ? 0 : body.hashCode());
		result = prime * result + (isExists ? 1231 : 1237);
		result = prime * result + ((vars == null) ? 0 : vars.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Quantifier other = (Quantifier) obj;
		if (body == null) {
			if (other.body != null)
				return false;
		} else if (!body.equals(other.body))
			return false;
		if (isExists != other.isExists)
			return false;
		if (vars == null) {
			if (other.vars != null)
				return false;
		} else if (!vars.equals(other.vars))
			return false;
		return true;
	}
}
